Editor's Note: This excerpt is from Chapter 7 of Care & Management of Horses by Heather Smith Thomas. The book is available from www.ExclusivelyEquine.com.

Fall Care

Rainrot
Rainrot (rain scald) is a skin problem that often appears during wet weather. Typical signs include very sensitive skin, clumps of hair coming off, and raw spots or crusty patches on the horse's back. After a rain you may see the horse's hair standing up in an odd pattern on portions of the body that got wet and where water ran down off the horse's sides. As you run your hand over the horse, you might feel heat and his back may be sore. By the next day he may have tight scabs on the sensitive areas. The scabbing may be a light peppering of small bumps, or the whole area may be a painful sheet of crusty, scabby skin.

The scabby bumps and crusts tend to be located in the runoff patterns on the horse's back and body, such as down the flanks and over the shoulders, back, rump, and neck. A heavy rain that wets the whole horse may cause bumpy crusts over most of the body, while a light rain causes only scattered patches. You may first notice the problem when brushing the horse. In early stages it is easier to feel the emerging bumps than to see them, and the bumps may come loose as you rub. They may be hot and tender and the horse may be sensitive when you brush him. As the disease progresses, the bumps become more raised and tufts of hair stand erect.

Rainrot is caused by the bacterium, Dermatophilis congolensis, which seems to have characteristics of both fungi and bacteria. It normally lives in the soil (dirt and mud of a pen or pasture) and is present in dust particles. The combination of water and dirt, such as when a dusty horse gets wet, makes an ideal environment for this opportunistic invader. This microbe can live in a dormant state within the skin for long periods. If the skin is compromised in some way, such as prolonged wetting by rain or high humidity, moisture enables dormant microbes from earlier lesions to establish new infection sites.

Rainrot is rarely a problem in dry weather. Best prevention is to keep horses clean and dry. If rainrot is a recurring problem, regular grooming, with periodic vacuuming to get as much dust and dirt as possible out of the hair, and a bath twice a month with a medicated shampoo can prevent this skin problem.

A common scenario for rainrot development is a period of rain following a dry, dusty spell. The dusty conditions fill the horse's coat with dirt (especially if he rolls), covering the skin with the microbe-laden particles. The rain then provides moisture for the organism to multiply. The problem often continues into winter if weather stays wet. A long, thick winter coat provides ideal conditions for the organism to keep multiplying.

Rainrot does not occur as much in stabled horses as in outdoor horses because they don't get the chance to roll in the dirt and pick up the microbe. The disease also occurs less frequently in horses that are regularly brushed, keeping the skin free of dust and dirt that might harbor the microbe. Sweat, skin secretions, dirt, and manure in the hair of an unbrushed horse can combine with moisture to get the organism started. Some horses seem more susceptible to rainrot infection. If kept on pasture or in a dusty paddock, they tend to develop the problem every year.

Rainrot is not contagious; it is spread by organisms in dirt and dust rather than by direct contact with an infected horse. It may appear in several horses at the same time, however, if they are kept in the same environment. Rainrot can be spread from one horse to another by dust and dirt on grooming tools and saddle pads. Don't use the same brushes or tack on more than one horse. You may want to disinfect grooming tools occasionally with a mixture of one part bleach and three parts water.

Treatment of rainrot consists of cleaning skin and hair with an iodine shampoo (or human dandruff shampoo or an antiseptic pet shampoo). You may have to shampoo the horse daily for seven to ten days (then several times a week) to get rid of bacteria-laden dirt in the hair coat. Massage the skin as you wash it, gently working loose the scabs and crusts. Leave the shampoo on for five to ten minutes before rinsing it off so the iodine has time to do some good. You can follow the shampoo and rinsing with a diluted iodine solution (one part povidone iodine to ten parts water) and leave it on the horse to dry.

After the horse is clean and dry, apply a mixture of equal parts tamed iodine (povidone iodine, such as Betadine, which is not as harsh as tincture of iodine) and mineral oil to affected areas (or an ichthammol salve--ointment made from a coal-tar base). The tamed iodine kills bacteria, and the mineral oil soothes raw spots and softens crusts, making removal of scabs easier next time. Never use iodine undiluted on the horse's skin or it may cause burning and irritation. Most horses tolerate diluted iodine with mineral oil, however. The oil leaves a coating on the hair that lasts several days (until next bathing), keeping the iodine in contact with the affected area longer.

Some veterinarians recommend a course of antibiotics, starting at the beginning of symptoms, to halt the infection before it gets well started. Often this halts the problem before it progresses to hair loss. Some cases of rainrot run their course and heal without treatment, but it takes longer. Serious infections should always be treated to prevent complications and scarring.

Unhealthy Edibles
Fall brings ripe seeds and fruits and after frosts some wilted leaves. Some of these can harm or kill if eaten by horses. Horses pastured near apple trees may overeat apples if some fall into the pasture or paddock. Under normal conditions a horse may not suffer adversely except for loose bowel movements, but if he is ridden, the combination of apples and exercise stress may cause colic. This is especially true with crab apples. A horse can develop very painful colic soon after he starts working if he has eaten many crab apples. It's much safer to make sure your horse does not have access to these.

Even more dangerous are acorns. Horses usually won't eat them unless pastures get dry in late summer or forage is short. A horse can die within twenty-four hours after eating a large quantity of acorns. An affected horse becomes depressed and weak, goes off feed, and colics. Horses should be removed in late summer or early fall from pastures containing oak trees, or fed hay if pasture is dry or short. Hungry horses should not be put into pastures with oak trees. If a horse recovers from acorn poisoning, putting him in such a pasture again is not safe because he may be addicted to acorns and seek them out.

Another danger is wilted leaves from certain trees. Red maple and wild cherry (chokecherry) are two of the most deadly; chemicals in their wilted leaves adversely affect oxygen-carrying capacity of the blood. Wilted red maple leaves can be toxic for at least thirty days. About eighteen to twenty-four hours after a horse eats the leaves, he may become depressed, the mucous membranes (gums and eyelids) become pale yellow or brown, and urine becomes dark or red.

After a frost, wilted chokecherry leaves contain cyanide. Death from eating these can occur within minutes or hours. The horse has rapid, labored breathing, red to blue mucous membranes, weakness and muscle tremors, and goes into convulsions. A mild case may recover; a more serious case can be treated, but the horse may die before your veterinarian arrives. It's best to make sure your pastures and paddocks contain no red maple or chokecherry trees within reach of horses. When riding or camping with horse in the fall, keep in mind that wilted fallen leaves of these trees can be deadly. Don't let a horse browse on trees or downed branches, nor graze underneath the trees where he might nibble fallen leaves.

Routine Fall Care
If a horse will not be ridden in winter, his shoes should be removed and his feet trimmed appropriately. Instead of taking the hoof wall down to the sole, leave a fraction of an inch of wall so the horse will not be walking on his soles and become tender. The outer edge of the wall should be well smoothed and beveled--a rounded edge is less apt to chip, crack, or break. If a horse is barefoot on winter pasture, feet should be routinely cleaned, checked (to prevent thrush and other wet-weather problems), and retrimmed as needed. All too often feet get neglected when unshod. Hoof walls keep growing, however, and must be kept trimmed to proper length to prevent damage.

Fall deworming is important; winter is usually when internal parasites do the most damage and rob the horse of vital nutrients. By fall the worm eggs and larvae eaten during spring and summer have matured and are living in the digestive tract unless you have kept horses on a good deworming schedule.

If you get cold weather during winter, make sure one of your fall dewormings is targeted for bots. In warm climates bot flies are active through winter, and control of these parasites must be constant and on going. In cold climates, however, there are no more flies after killing frosts. The eggs laid on the horse's hair can continue to infest him after cold temperatures have killed off the adult flies, however, so any bot eggs found on the horse in the fall should be removed. Deworm the horse for bots to eliminate all the immature forms in his mouth and digestive tract.

Fall is also a good time to check a horse's teeth, especially older horses that may have trouble chewing their food adequately. Correcting dental problems in the fall (such as sharp hooks on teeth, making chewing painful) will ensure that a horse gets the most good from his winter feed and will be less likely to lose weight.

About the Author

Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog, www.heathersmiththomas.blogspot.com, she writes a biweekly blog at http://insidestorey.blogspot.com that comes out on Tuesdays.

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